The relationship between vomiting and seizures is complex. While the physical act of vomiting does not routinely cause a seizure in a healthy individual, both symptoms can arise concurrently from a shared underlying illness or neurological pathways. In many cases, vomiting is an effect of brain activity, not the cause of the electrical event itself.
Physiological Triggers of Seizures During Vomiting
The intense physical exertion of vomiting, known as retching, can momentarily destabilize the brain’s environment. Forceful straining increases pressure within the chest and abdomen, impeding blood return to the heart. This transient reduction in cardiac output decreases blood flow to the brain, causing a temporary lack of oxygen or a sudden drop in blood pressure. This process is a form of situational syncope, which may include convulsive movements (convulsive syncope) that are not true epileptic seizures.
Massive fluid loss from acute, prolonged vomiting rapidly shifts the body’s internal chemistry. A sudden loss of fluids can result in an electrolyte imbalance, especially hyponatremia (low sodium levels). When sodium levels drop too quickly, brain cells can swell, creating an unstable electrical environment. This electrolyte disturbance directly lowers the seizure threshold, acting as a potent trigger for a provoked seizure.
Underlying Medical Conditions That Cause Both
The most significant link between vomiting and seizures is when they manifest as symptoms of a shared systemic or neurological disorder. Central Nervous System (CNS) infections, such as meningitis or encephalitis, are prime examples. Inflammation or infection of the brain tissue often causes fever, severe headache, and vomiting, while direct irritation of the brain leads to seizures.
Metabolic disorders are another major category where these two symptoms converge. Conditions causing a buildup of toxins result in both vomiting and neurological dysfunction. For instance, uremic encephalopathy (severe kidney failure) and hepatic encephalopathy (severe liver failure) cause neurotoxins to accumulate, leading to nausea, confusion, and seizures. Vomiting can also signal hypoglycemia (low blood sugar), which starves the brain of energy and is a known cause of seizures.
Increased intracranial pressure (ICP), often caused by a brain tumor or hemorrhage, is a direct neurological cause of both symptoms. The pressure irritates the brainstem’s vomiting center, causing projectile vomiting. As the pressure rises, it compresses brain tissue, disrupting normal electrical activity and resulting in a seizure.
Toxic exposure or medication side effects can also trigger this combination of symptoms. Serotonin syndrome, a reaction to certain medications like antidepressants, can cause symptoms ranging from vomiting to high fever and seizures. Furthermore, certain drugs, including antibiotics or stimulants, can directly affect brain chemistry to cause seizures and simultaneously induce vomiting due to systemic toxicity.
Vomiting as a Symptom of a Seizure
The reverse relationship, where the seizure itself causes the vomiting, is a well-documented phenomenon known as ictal vomiting. Ictal vomiting occurs during the seizure or immediately before or after the electrical event. It is an autonomic symptom, indicating that the abnormal electrical discharge is impacting brain areas that control involuntary functions, such as digestion.
This seizure activity most often originates in the temporal lobe, involving structures like the amygdala. Electrical activity in these regions can activate the brainstem’s emetic center, causing nausea or vomiting. For some individuals, vomiting or a rising “epigastric sensation” may serve as an aura, or warning sign, that a seizure is about to occur. This is a specific type of focal seizure where the electrical activity is limited to a particular brain area. In rare instances, particularly in children, recurrent vomiting can be the main symptom of a seizure disorder, sometimes referred to as abdominal epilepsy.
Recognizing When to Seek Emergency Care
Any new onset of seizure activity or the combination of vomiting and seizures requires immediate medical evaluation. Emergency services should be called if a seizure lasts for five minutes or longer, or if a second seizure occurs shortly after the first. A seizure that occurs in someone who is pregnant, diabetic, or has a known injury also warrants immediate attention.
Certain combinations of symptoms accompanying vomiting indicate a severe underlying problem that needs urgent care. Seek immediate help if vomiting is accompanied by signs of severe infection or neurological distress:
- Severe, persistent headache
- Stiff neck
- High fever
- Confusion or lethargy
- Difficulty staying awake or any significant change in mental status
Persistent vomiting that prevents the individual from holding down fluids also requires prompt emergency intervention. This is especially true if there are signs of severe dehydration, such as intense thirst, dizziness, or dark urine.